1. Field of the Invention
The present invention relates to transistor of semiconductor device and method for manufacturing the same, and more particularly to improved transistor of memory device and method for manufacturing the same which provides a high speed and high integrated device by preventing deterioration of the characteristics of the device resulting from increase of impurity concentration as the integration of the device is increased.
2. Description of the Background Art
As the integration of a semiconductor device has been increased, integration of a DRAM has increased. However, the refresh time of the DRAM is almost double in each generation because of a high speed and low power requirements.
As the density of a memory device continuously increases, the concentration of impurities implanted into a substrate must be increased to minimize short channel effects, threshold voltages and leakage currents. However, the increase of the concentration of impurities results in increase of junction electric intensity, which generates short channel effects and leakage currents.
Moreover, the increase of concentration increases junction capacitance, thereby reducing the operation speed of the device.
As described above, in the conventional transistor of the semiconductor device and a method for manufacturing the same, the characteristics of the device is degraded due to the increased concentration of impurities implanted into the substrate, thereby making the achievement of the high operation speed and high integration of the semiconductor device more difficult.